LOWELL, Mass. -- Sydney Corcoran, pictured in one of the iconic images of the Boston Marathon blast, had already cheated death once.

While crossing a busy street at Salisbury Beach, Mass., in June 2011, Corcoran was struck by a car driven by a senior citizen. The accident left her with severe injuries, including a fractured skull.

But Sydney, 18, a Lowell High School senior bound for Middlesex Community College this fall, dug deep and fought to survive.

On Monday, shrapnel from one of the bombs that exploded during the Boston Marathon shredded both of Sydney's legs, leaving her with deep arterial injuries, her older brother. Tyler Corcoran spoke during an interview Tuesday morning in the kitchen of the family's home in Lowell.

Sydney, with her mother, Celeste, and father Kevin, were in Boston to watch her aunt, Carmen Accabo, finish the storied event. Celeste, too, was struck by shrapnel, and had both legs amputated below the knee overnight, Tyler said.

Kevin suffered only minor injuries. He was at the Boston Medical Center bedsides of both his wife and daughter Tuesday, said his brother, Tim Corcoran, of Rhode Island.

"My brother is just heartbroken, just devastated," Corcoran said as he drove up Interstate 95 to be with his brother.

Like his uncle, Tyler was also heading to the hospital today to be with his father, mother and sister. Tyler had planned to be with his family at the finish line Monday, but the Middlesex Community College student was scheduled to meet with a study group.

"I was supposed to be there," said Tyler, fighting back tears. "I didn't even think this whole thing was real until my phone started ringing like crazy later in the afternoon."

The explosive devices were detonated seconds apart, several hundred feet west of the finish line near the Boston Public Library, both near the Boylston-Exeter streets intersection. It's unclear precisely where the Corcoran family stood. Tyler said his father described a surreal scene of gusts of wind generated by the blasts and "debris flying everywhere." Three people were killed, including an 8-year-old Dorchester boy, and nearly 200 were injured, many seriously.

"My father said everyone seemed in a daze. He looked down and saw my mom and her eyes were open. Once he realized she was alive, he noticed both her legs hanging on by skin. He asked a guy for a belt."

Tyler said her sister was just nearby. "Her legs were hit pretty bad," said Tyler.